loesche technology - always a step ahead: loesche mills for cement raw material
DESCRIPTION
Cement raw material has been almost exclusively ground in roller mills (vertical air-swept grinding mills) since the second half of the 20th Century. Loesche was and is the pioneer of this technology. Hundreds of Loesche mills have been used in the cement industry across the world to the present day. They operate with two, three, four and six rollers.TRANSCRIPT
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Loesche-Millsfor
cement raw material
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Cement raw material has been almost exclusively
ground in roller mills (vertical air-swept grinding mills)
since the second half of the 20th century. Loesche
was and is the pioneer of this technology. Hundreds
of Loesche mills have been used in the cement indus-
try across the world to the present day. They operate
with two, three, four and six rollers.
1928 The first spring-loaded air-swept grinding mill in
the world, constructed by the original company
Curt v. Grueber Maschinenbau-Anstalt, Teltow
near Berlin, is launched onto the market under
the name Loesche Mills and has 2 grinding
rollers. It already has all the essential features
of modern air-swept vertical grinding mills built
today. Even the first Loesche mills had an inte-
grated dynamic classifier. Several examples of
this are deployed in Klingenberg, Europe’s first
coal dust-fired large-scale power plant in Berlin
for coal grinding with a raw coal rate of approx.
12 t/h.
1934 Loesche mills are increasingly also used world-
wide for limestone and cement raw material.
1937 400 Loesche mills have already been sold for
coal, phosphate and cement raw material.
1939 The largest Loesche mill at this time is an
LM 16 with two steel spring-loaded rollers, a
grinding track diameter of 1,600 mm and pro-
duct throughput of 22 t/h.
1948 The company in Teltow is nationalised; the
company is newly established under the name
Loesche KG in Düsseldorf (West Germany).
1949 – 1960 Loesche mills supplied in the sizes
LM 16 to LM 20 in modern welded construction
with two steel spring-loaded rollers and pro-
duct throughputs up to approx. 55 t/h.
1961 – 1970 Development of 2-roller Loesche mills
in the sizes LM 22 to LM 28 with the world
novelty of a hydropneumatic spring assembly
system for product throughputs up to 140 t/h.
Loesche technology – always a step ahead
Loesche Mill Type LM 46.4,
Lengerich, Germany, 2003
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1971 Introduction of a modular system in mill
construction: creation of replacement groups
of components such as rollers, rocker arm and
hydropneumatic spring for constructing mills
with 2, 3 and optionally 4 rollers of the same
size. The first LM 30.4 and LM 32.4 4-roller
mills are sold and have product throughputs of
178 t/h and 215 t/h.
1973 Sale of LM 36.4 und LM 43.4 mills with product
throughputs of 260 t/h and 425 t/h.
1989 Sale of the first LM 50.4 with a throughput of
490 t/h.
1996 Sale of the first LM 63.4 with a throughput of
800 t/h.
2005 Sale of the first 6-roller Loesche mills LM 60.6
with a throughput of 740 t/h
2006 – 2008 14 Mills Type LM 69.4 and LM 69.6 with
product throughputs of up to 1200 t/h are sold.
In the 1930s Loesche mills are used to grind cement
raw material for the first time. The major breakthrough
came at the start of the 1960s when rotary kilns
with heat exchangers (dry process) are introduced.
The following Loesche technological features make
the deployment of these mills so successful in the
cement industry:
• Lowspecificenergyconsumption
• Lowpressurelossthroughlargecross-
sectional flow areas in Loesche mills
• Minimalsoundemissionssothatnosound
insulation measures are required
• Rapidreactiontofluctuatingrawmaterial
qualities
• Rapidreadjustmenttodifferentproduct
qualities
• Useofthekilnexhaustgasesfordry
grinding and as a transport medium for the
final product to dust separators
Loesche Mill Type LM 45.4 roller mill, Elmadag, Turkey, 1995
Loesche Mill Type LM 63.4,
Hereke, Turkey, 2002
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Quality and reliability right from the start are the glob-
ally recognised benefits to be derived from Loesche
grinding plants. As early as 1928, when the first
Loesche mill came onto the market, the grinding
principle of the vertical roller grinding mill, with a
driven grinding track and spring-loaded rollers was
shown to be particularly energy-efficient and reduced
the use of natural resources. These advantages of
Loesche mills will become ever more important in
the light of increasing plant size and the obligation to
make more careful use of primary energy.
Moreover, the high product throughputs of Loesche
mills (up to 1,300 t/h for cement raw material and
already 350 t/h for cement clinker and granulated
blast furnace slag) result in considerably reduced
investment costs compared to two smaller grinding
plants.
Loesche is a competent partner for its customers
from the initial sale to customer service and from
punctual project planning to the handing over of the
plant. Our maxim is “Every Loesche grinding mill
must be a reference mill!”
Our competence is founded on the following
key features:
• Tailor-madeplantconceptsfromplanningtocom-
missioning, based on our own experience com-
bined with customer wishes
• Individual problem solutions through optimised
process technology
• Rational solutionswith simultaneous planning of
cement clinker/granulated blast furnace slag mills
and raw meal mills through the use of exchange-
able components for all models of mill, extending
to the use of identical gear drives
• Closecooperationwithsuppliersofrotarykilnsin
line with customer wishes
• Customerservice:plantoptimisationandadvice
in the case of further technical developments
• Long-term delivery capability when supplying
spare parts
• Certification in accordance with EN ISO 9001:
2008.
Benefits to customers and customer satisfaction
Loesche Mill Type LM 60.4,
Ras Al-Khaimah,
United Arab Emirates, 2005
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Shipment for further processingTransport to the port
Assembly of the grinding table Mill with classifier under constructionAssembly of the lower part of the mill
Grinding table of an LM 69 in the foundry
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Working principle, construction and function of Loesche mills
Working principle
The material to be ground is crushed between the
rotating grinding track and the individually guided
grinding rollers.
Grinding is carried out primarily through the applica-
tion of compressive force. A small amount of shear
force supports the displacement of crystalline layers
in the raw material. This effect occurs through coni-
cal rollers whose axes are inclined at 15° compared
to the horizontal grinding track. As already demon-
strated through comparative studies in the 1930s,
this permits ideal fine grinding and at the same time
ensures minimum wear.
A higher specific grinding pressure is applied com-
pared to coal grinding and a lower specific grinding
pressure is applied compared to the fine grinding of
clinker and granulated blast furnace slag.
Hot gases are added in the dry-grinding process to
evaporatematerial moisture. Use is predominantly
made of the exhaust gases from the rotary kilns, the
heat exchanger or the cement clinker cooler. If none
of these sources are available or the heat content of
these exhaust gases is insufficient, Loesche’s own
hot gas generators are deployed. In the classifier
above the grinding chamber the ground product is
separated from the grit which then falls back onto the
grinding track for renewed grinding.
Construction
The familiar basic principle of the modular system
patented in 1970 is applied to Loesche mills with
two, three, four and six rollers. The rollers together
with their lever systems, hydropneumatic springs and
hydraulic control systems make up a functional unit.
Large or small modules with a different number of
rollers (between two and six) can be deployed in the
same mill sizes (grinding table diameter). This makes
it possible to customise the product to meet specific
customer requirements.
The following features characterise Loesche
technology:
• Thesupportandpreciseguidingoftherockerarm
roller system with its roller bearings takes place in
a pedestal with integrated spring system.
• Hydropneumaticspringloadingoftherollerrocker
arm unit with integrated mechanism to lift the
rollers serves as an aid for the mills when starting
up with a filled grinding track.
• The rollers are connected in pairs to a common
hydraulic unit (except in the case of 3-roller mills).
• An almost parallel grinding gap is maintained
between the grinding rollers and the grinding
plates during the entire service life of the grinding
parts.
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Loesche Mill Type LM 69.6, Idhan, United Arab Emirates, 2009
View of the grinding chamber of an LM 69.6 Rollers of an LM 69.6 Mill gearbox
Gas spring system Rocker arm in working position Hydraulic cylinder
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Mill function
The cement raw material is fed via a rotary feeder
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and falls via the chute 1
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onto the centre of the
grinding bed 1
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. Free ferrous foreign objects are
separated out from the feed material magnetically
before reaching the rotary feeder 1
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and removed via
a diverter gate. A metal detector operates in a simi-
lar way and ensures the separation of non-magnetic
metal parts. The material to be ground moves on the
grinding track towards the edge of the grinding table
under the effect of centrifugal force and in this way
passes under the hydropneumatically spring-loaded
grinding rollers 1
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.The material that has been drawn
in is ground in the material bed in the gap between the
rollers and grinding track. The rollers 1
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are displaced
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. As a
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spring rod and pistons from the hydraulic cylinder
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is moved. The piston displaces the hydraulic oil
from the cylinder into the gas-filled bladder accumu-
latorunit.Nitrogen-filledrubberbladdersintheaccu-
mulator units are compressed and act as gas springs.
The gas springs can be set to be harder or softer by
selecting the gas pressure in relation to the hydraulic
operating pressure, depending on the fracture behav-
iour of the material to be ground.
The ground material is subjected to centrifugal force
and rotates outwards and over the edge of the grind-
ing table. In the area of the louvredam ring 1
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which
surrounds the grinding table 1
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the stream of hot gas
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directed upwards captures the mixture of ground
material and material as yet not completely ground
and conveys this to the classifier 1
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.
Depending on settings of the classifier 1
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it rejects
coarse materials. This falls into the internal grit return
cone 1
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and then onto the grinding table 1
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for
re-grinding. The ground material passes from the
classifier and is conveyed from the Loesche mill with
the gas stream 1
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Foreign matter and small amounts of coarse material
fall through the louvre ring 1
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into the ring channel 1
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as reject material.
Scrapers 1
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connected to the grinding table trans-
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.
Cement raw material usually has differing degrees
of moisture content when extracted from the quarry.
As soon as the ground material leaves the grindin g
table in the area above the louvre ring 1
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, the water
contained in the working material evaporates sponta-
neously upon intimate contact with the hot gas stream.
Therefore the required mill outlet temperature of the
dust/gas mix of approx. 80 ° to 110 °C is already
achieved in the grinding chamber.
The mill is driven by an electric motor 1
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via a flexible
coupling 1
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and the mill gearbox via an output flange 1
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. A segmental thrust bearing in the top of the gear-
box absorbs the grinding forces.
The grinding rollers 1
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are hydraulically lifted from
the grinding track before the mill motor is started.
The mill can then not only be started empty but also
partially filled with a low starting torque. Metallic
contact of grinding parts on an empty or loaded mill is
prevented by automatic lifting of rollers via a grinding
bed depth control.
A so-called “auxiliary drive” for starting up a filled mill
at low revolutions is not required!
Servicing
Worn grinding parts, roller tyres and grinding track
segments can be simply and quickly replaced. The
rollers are retracted from the grinding chamber into a
vertical position using a retracting cylinder. Complete
rollers, roller tyres and grinding plates are then made
accessible to hoisting devices.
When grinding cement raw material the metallic
particles usually cause uniform wear throughout their
entire service life so that the mill throughput only
declines when mill parts are completely worn. Partial
wear may occur if, for reasons of cement chemistry,
free quartz sand needs to be used as concrete aggre-
gate. This can be offset by targeted hard facing in
the mill.
Loesche has the required know-how for in-situ weld-
ing using appropriate welding equipment.
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Mill selection sizing – models – dimensions – drives
Dimensioning parameters
The following standard parameters are decisive for
dimensioning Loesche cement raw material mills:
• GRINDINGPRESSURE
This lies between the minimum value for solid
fuels and the maximum value for cement clinker/
granulated blast furnace slag.
• MATERIALMOISTURE
The Loesche mill can process material with mois-
ture of up to 25%.
• PRODUCTFINENESS
The fineness of the final product is between 6%
and30%R0.09mm,dependingonthecomposi-
tion of the raw material.
• DRIVEPERFORMANCE
The specific energy consumption in the grinding
test is decisive for gearbox and motor sizing.
Models
• Mill sizes are identified according to the outer
effective diameter of the grinding track in decime-
tres [dm].
• Theidentificationisfollowedbyadigit,separated
by a full stop. This specifies the number of rollers
operated in the mill.
• The number and size of rollers is geared to
the required product throughput in conjunction
with the “Loesche performance factor” as well as
the product which is influenced by factors of
grindability, moisture and fineness. The required
gas stream is decisive for the housing dimension-
ing of mill and classifier.
• The Loesche cement and raw meal mills are
constructed in a modular fashion. Modules are
understood as units comprising rollers, rocker
arms and roller-related spring components with
their pedestal. This is arranged from between 2
and 6 times around a grinding table as required.
Dimensions
• The coordinates of the grinding table diameter
and number of rollers can be read off from
the following table. The x-coordinate indicates
which product throughputs can be generated
using the respective mills. The width of the fields
is a measurement of the output factor (see above).
• The dimensions H, A and D in turn describe
the height of mills with classifier, the footprint
diameters and the overall space required, taking
a service area (for replacing grinding parts) into
consideration.
Drives
An electric motor serves as the drive. It drives a plan-
etary gearbox using a torsionally flexible coupling.
The drive shaft lies horizontally, the vertically mount-
ed flanged output shaft rotates in a horizontal plane.
The gearbox contains a segmental thrust bearing that
accommodates the grinding force at the top of the
housing. Loesche mill gearboxes are developed in
cooperation between Loesche GmbH and reputable
gearbox manufacturers. The dynamic safety factors
are suitably chosen for the application. Decades of
experience operating Loesche mills determine the
design of the (mill) gearbox and their peripherical
equipment, bearing in mind all climatic conditions.
Modern gearboxes today are constructed in a modu-
lar manner in the same way as Loesche mills. Torque
split ensures a reduction in the rotating masses and
simultaneous multiple use of machine construction
elements in gearboxes with different sizes and
performance.
A lubrication unit ensures that adequate oil is
supplied to the gear teeth, the shaft bearings and
the segmental thrust bearing. Filters and cooling
equipment condition the oil. Electrical and hydraulic
instruments that are monitored in the customer’s PLC
guarantee safe operation.
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0 200 400 600 800 1000 1200 1400
LM 69.6
LM 60.6
LM 56.4
LM 53.6
LM 48.4
LM 46.4
LM 45.4
LM 41.4
LM 38.4
LM 35.4
LM 38.3
LM 31.3
LM 31.2
LM 24.2
LM 21.2 A
D
The modular construction principle of gearboxes
permits further increases in performance in line with
the current state of the art without the need to
develop a new construction concept.
The Loesche mill does not require a motor with
increased starting torque. Since the rollers are raised
hydraulically, the breakaway torque for the filled mill
only comprises 40% of the full load torque. This
starting torque can be achieved by a “standard
motor” without a problem.
The installed motor power is sized according to the
energy requirements of the mill. This is established in
the test plant using a grinding test. The next suitable
commercially available motor is selected and recom-
mended to the customer.
* Remark:Alldimensionsareguidelinevaluesandcannotbeconsi-dered as the basis for a binding planning.
Product throughput [t/h]
Product rate [t/h] as function of the LM size
FinenessFine Coarse
Difficult EasyGrindability
H[m]* A[m]* D[m]*
29.9 17.0 18.0
21.1 15.0 17.0
21.0 12.0 17.0
18.4 12.0 17.0
17.8 10.5 15.0
16.7 10.0 14.0
15.4 9.0 13.0
14.9 8.0 12.0
13.0 8.0 12.0
13.0 7.5 12.0
13.4 8.0 12.0
11.7 7.0 11.0
11.4 7.0 11.0
10.7 6.5 11.0
9.4 6.0 10.0
~6,900 kW
~5,300 kW
~4,200 kW
~3,600 kW
~3,100 kW
~2,600 kW
~2,000 kW
~1,900 kW
~1,750 kW
~1,600 kW
~1,400 kW
~1,200 kW
~700 kW
~600 kW
~450 kW
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Cement raw material; deposits
Cement raw material is principally a compound made
of limestone and argillaceous rock, which undergoes
mechanical and thermal treatment to create cement
clinker. The geological formation, material composi-
tion and water content influence the grinding dryness
and energy requirements.
The raw materials are classified according to their
origin into
•natural mineral raw materials and
•synthetic mineral materials
that are by-products or waste products from other
branches of industry deploying raw materials.
The suitability of natural and synthetic mineral raw
materials for manufacturing binding agents is primar-
ily determined by their chemical composition.
The following fields are chiefly used for the provision
of the most important components:
•Carbonate fields,
consisting for example of shell limestone, white
Jura, chalk etc.
•Silicate aluminate deposits,
consisting for example of sandstone and argilla-
ceous rock, magmatic and metamorphic rocks etc.
For a good and fast reaction during the firing process
it is more favourable to use those materials whose
composition is by nature closer to the desired chemi-
cal compound.
The compositions of raw material compounds used
in practice can be most easily represented using the
tablefromLABAHN&KOHLHAAS(1982).
Chemical composition of cement raw material; ignition loss-free.
[LABAHN&KOHLHAAS,1982]
MINERAL OXIDE min. and max. mass[%]
LIMESTONE CaO 60–69
SILICATE SiO2 18 – 24
CLAY Al2O3 4 – 8
FERRICOXIDE Fe2O3 1 – 8
MAGNESIUMOXIDE MgO <5.0
POTASSIUMOXIDE/
SODIUMOXIDEK2O;Na2O
<2.0
SULPHURTRIOXIDE SO3 <3.0
Loesche_Zement_Rohmaterial_11-09.indd 12 17.09.12 11:31
13
AccordingtoLabahn&Kohlhaasthefollowingterms
are common for the raw materials used arranged with
diminishing CaCO3 content:
• Purelimestone >95M.–%CaCO3
• Marlylimestone 85–95M.–%CaCO3
• Limemarl 70–85M.–%CaCO3
• Marl 30–70M.–%CaCO3
• Argillaceousmarl 15–30M.–%CaCO3
• Marlyclay 5–15M.–%CaCO3
• Clay <5M.–%CaCO3
Cement raw materials require a CaCO3 content of
between 74 and 79 M %. The desired raw material
composition is rarely found in a natural raw material.
For this reason materials containing SiO2 and ferric
oxide as well as fluorites must be used as correcting
materials to precisely adjust the required raw material
compounds and to improve sintering.
Some of these grinding materials additives are highly
abrasive and lead to the disproportionate wear
of grinding parts, areas of machines and in ducts
through high speeds of gas-solid mixtures. Loesche
takes suitable protective measures against wear
when materials of this nature are used.
Loesche_Zement_Rohmaterial_11-09.indd 13 17.09.12 11:31
14
The homogeneity and fineness of the cement raw
meal also plays an important role in the downstream
sintering process in addition to the correct chemical
composition of the raw meal mixture.
There are high demands with respect to the permit-
ted residual moisture in the ground product.
The residual moisture (max. 0.5 M %) must be
just as homogeneous as the distributed chemical
components.
This also means that where water content varies, for
example in the case of limestone and clays, the
residual moisture content of each component of the
finished material must be approximately the same.
The process control system of the Loesche mill
guarantees this.
CEMENT RAW MATERIAL
Tests on materials to be ground
The characteristics of the cement raw material must
be known in order to determine the size of the mill
and classifier. The material properties are examined
in the Loesche test plant. Ideally the customer sup-
plies the test plant with a representative sample of
the cement raw material compound as used in his
factory. If a quarry has not yet been opened in the
case of new construction projects, specified quanti-
ties of individual components are supplied and
chemically analysed. Their moisture is measured and
under some circumstances adjusted. A quantity of
feed material amounting to at least 1.5 t is prepared
from the supplied or manufactured raw material com-
pound. If the supplied grain size is too coarse for the
Loesche laboratory mill, the required feed material
grain size is generated in the Loesche laboratory
crusher in an intermediate stage before grinding. The
raw material is then completely ground, dried and
classified in the Loesche test plant mill in continuous
operation.
The test grinding delivers the following representa-
tive results:
• Loeschegrindabilityfactor“MF“;
• Loeschefinenessfactor“FF“;
• Moisturefactor“WF”withwatercontentof>8%;
• Specificenergyconsumption“e”[kWh/t];
• Wearfactor“VP”.
The appropriate Loesche mill is determined using
these parameters and standard charts.
Notwithstandingthesestandardisedmethods,other
decisive variables flow into the dimensioning of the
mill, the classifier and also the mill fan, such as
extremely high grinding material moisture or very
high differences in the case of grindability factors of
individual raw material components.
Loesche Mill
Type LM 38.4,
Testi, Italy, 2004
Loesche_Zement_Rohmaterial_11-09.indd 14 17.09.12 11:31
15
Until the end of the 1950s Loesche mills were
deployed in the power station industry as coal direct
firing mills for steam furnaces in model sizes up to
LM 16. In the limestone and fertiliser area mill sizes
of up to LM 18 with product throughputs of up to
40 t/hwere common. Relatively few verticalmills
are still being used for grinding cement raw material
in cement works. Most can be found in cement
works with shaft kilns. The biggest mill in 1960 was
an LM 20 with approx. 50 t/h product throughput
and drive power of 400 kW.
The need for Loesche mills for grinding cement raw
material skyrockets at the start of the 1960s. The
reason for this trend is the technological development
in the cement manufacturing process which moves
away from the energy-intensive wet procedure to the
semi-dry process and ultimately to the dry process
with precalcination. As a result the kiln throughput
increased dramatically with simultaneous significant
reduction in specific energy consumption.
From the beginning Loesche develops mill sizes that
are adapted to the throughput of the cement rotary
kiln.
The mills launched onto the market satisfy the
following requirements:
• Mill capacities adapted to the rawmeal require-
ments of the rotary kilns and which permit parallel
operation of the kiln and mill.
• Millsizesthatpermittheparalleloperationofakiln
with a mill, a concept that is specifically up to 30%
more cost effective than the parallel operation of a
rotary kiln with 2 roller mills! This Loesche phi-
losophy has been proven to be correct and is
today generally accepted by customers.
• Millswhichmakeidealuseoftheexhaustgases
of the rotary kiln for dry grinding and for transpor-
tation of the grinding materials with low specific
energy consumption [kWh/t].
• Grinding, drying, classifying in onemachine unit
through to the ground product with the required
grain distribution and residual moisture.
• Grindingplantswhichcanbequicklyadjustedin
line with the operational requirements of the firing
process.
Feed of the materials to be ground
The cement raw material is crushed up in the tradi-
tional manner and stored in raw material hoppers
according to components. From there it is propor-
tioned and added to the mill feed belt. The speed of
the conveyor belt can be regulated.
A belt magnet and a metal detector for separating
larger metallic parts of foreign matter are situated in
the path of the material to the mill.
The material then passes into the mill hermetically
sealed through a rotary feeder or a gate feeder. The
rotary feeders are specially adapted to the properties
of the feed material. Thus oversized pieces, so-
called “fish” or tree roots are used as reference for the
maximum filling level of the cells. The calculated fill-
ing level of the chambers is less than 40 % of
the pocket volume in order to prevent the rotor
clogging.
Both types of gate can be heated using process
gas in the case of moist feed material.
Rotary and gate feeders are equipped with wear
protection.
Grinding and classifying
The raw material is ground and dried in the mill. Mills
with 2 rollers have one hot gas entry channel, while
those with three and four rollers have two and mills
with six rolls have four. The process gas is distributed
from there uniformly by means of guide vanes into the
grinding bed chamber. When it leaves the grinding
table the ground material together with the process
gas, which has since been cooled by water evapora-
tion to below 100°C, is fed to the classifier on the mill.
The powdered ground product leaves the classifier
and is separated in a downstream filter or a combina-
tion of cyclone battery with (smaller) filter. Separated
grit falls back onto the grinding track along with fresh
material.
Complete grinding plants with components
Loesche_Zement_Rohmaterial_11-09.indd 15 17.09.12 11:31
16
Reject treatment
The reject material passing through the louvre ring is
automatically cleaned out and transported off via an
airtight encapsulated conveyor and bucket elevator.
The flow of feed material to the mill, which is the sum
of the fresh material and reject material, is maintained
at a constant level by the proportioning system.
Mill fan
The mill fan requires no wear protection due to the
high efficiency of the dust separator. It is generally
equipped with an inlet vane control and / or a variable
speed drive.
Process and measuring and control equipment
The heat required to dry the material to be ground is
controlled by the process control system such that
that gas temperature at the mill outlet remains
constant. The preferred source of the heat energy
required is provided by the exhaust gas flow of the
rotary kiln. If this is insufficient, heat must be
provided from other sources. A separate hot gas
generator (LOMA combustion chamber) as well
as gases from other processes such as preheated
waste gases, clinker cooler exhaust gases and
exhaust gases from diesel generators etc. are
suitable for this.
Part of the process gas is recirculated upstream of
the dust separator in order to utilise its heat content.
The remaining part is exhausted via a stack. A fresh
air flap is located in the recirculation gas duct to the
mill. Where exhaust gas temperatures reach over
100°C at the mill outlet cold fresh air can be sucked
in from the atmosphere; this fresh air reduces the
temperature of the mill exhaust gas to the desired
temperature. The upper temperature limit is
determined by the thermal resistance of the filter
(bag material), the lower temperature limit by the
dew point of the stream of dust gas. Levels must
under no circumstances fall below this lower limit in
order to prevent condensation.
Loesche_Zement_Rohmaterial_11-09.indd 16 17.09.12 11:31
16 18
1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 281
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
Reject treatment
The reject material passing through the louvre ring is
automatically cleaned out and transported off via an
airtight encapsulated conveyor and bucket elevator.
The flow of feed material to the mill, which is the sum
of the fresh material and reject material, is maintained
at a constant level by the proportioning system.
Mill fan
The mill fan requires no wear protection due to the
high efficiency of the dust separator. It is generally
equipped with an inlet vane control and / or a variable
speed drive.
Process and measuring and control equipment
The heat required to dry the material to be ground is
controlled by the process control system such that
that gas temperature at the mill outlet remains
constant. The preferred source of the heat energy
required is provided by the exhaust gas flow of the
rotary kiln. If this is insufficient, heat must be
provided from other sources. A separate hot gas
generator (LOMA combustion chamber) as well
as gases from other processes such as preheated
waste gases, clinker cooler exhaust gases and
exhaust gases from diesel generators etc. are
suitable for this.
Part of the process gas is recirculated upstream of
the dust separator in order to utilise its heat content.
The remaining part is exhausted via a stack. A fresh
air flap is located in the recirculation gas duct to the
mill. Where exhaust gas temperatures reach over
100°C at the mill outlet cold fresh air can be sucked
in from the atmosphere; this fresh air reduces the
temperature of the mill exhaust gas to the desired
temperature. The upper temperature limit is
determined by the thermal resistance of the filter
(bag material), the lower temperature limit by the
dew point of the stream of dust gas. Levels must
under no circumstances fall below this lower limit in
order to prevent condensation.
Loesche_Zement_Rohmaterial_11-09.indd 16-18 17.09.12 11:28
19 21
M
M
M
M
M
MM
M
M M M M
M
M
M
M
M
M M M MM M
M
M
1 1 1 1 1
2 2 2 2 2
3
45
6
3
6
7
8
9
10
11
12 12 12 12
13 13 13 13
14 15
13 13
16
17
18
19
20
21
22 25
26
23
24
27
28
29
4
1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 281
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
1. Material feed hopper 2. Weigh feeder 3. Transport conveyor belt 4. Metal detector 5. Over belt magnet 6. Diverter gate 7. Tramp metal bin 8. Rotary gate 9. Loesche mill10. Sealing air line with fan11. Water injection12. Cyclone13. Rotary valves14. Gas �ow measuring device15. Mill gas fan
16. Recirculation gas line with damper
17. Hot gas generator18. Reject system19. Bucket elevator20. Reject hopper21. Discharge conveyor22. Induced draught fan23. Shut-off valve at mill inlet24. Fresh air damper25. Bypass valve26. Butter�y valve at �lter inlet27. Kiln �lter28. Filter fan29. Stack
Structure:
1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
Grit return
1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
Guide vane
1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
Rotor with classifier blades
1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
Rotor shaft
1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
Housing
1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
Material feed chute
1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
Product discharge
Dynamic Loesche classifier LSKS
The classifier can separate particle sizes of up to
1 μm (and generate products with residues of
1% R 10 μm). The mechanical components of the
classifier in combination with process influencing
parameters can produce various particle size distri-
butions.
The LSKS classifier is able to operate both at high
selection efficiency for a narrow particle size distribu-
tion, as well as with a wide particle size distribution.
The gas / particle stream from the mill is passed to the
classifier chamber via a static guide vane device 1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
.
The gas-solids mixture flows through the adjustable
guide vane 1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
and is presented to the radially bladed,
concentrically placed, classifier rotor 1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
.
The rotor accelerates the gas-solids mixture tan-
gentially. The centrifugal force produced rejects the
oversize material.
Through selection of the rotor speed, in combination
with the gas stream and its direction of flow, the
required separation grain size can be adjusted within
a wide range.
A special feature of this classifier type is the conti-
nuous re-classification of the particle stream rejected
by the rotor. When the particles are thrown outwards
by centrifugal force into the annular gap between
static guide vane and rotor they are again subjec-
ted to the upwards/inwards directed gas stream. In
this way agglomerated particles can be more easily
separated, so that they follow the product stream as
single grains and do not fall back onto the grinding
table with oversize material as apparent oversize.
Loesche_Zement_Rohmaterial_11-09.indd 19-21 17.09.12 11:28
21
1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 281
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
Structure:
1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
Grit return
1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
Guide vane
1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
Rotorwithclassifierblades
1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
Rotorshaft
1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
Housing
1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
Material feed chute
1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
Product discharge
Dynamic Loesche classifier LSKS
The classifier can separate particle sizes of up to
1 μm (and generate products with residues of
1% R 10 μm). The mechanical components of the
classifier in combination with process influencing
parameters can produce various particle size distri-
butions.
The LSKS classifier is able to operate both at high
selection efficiency for a narrow particle size distribu-
tion, as well as with a wide particle size distribution.
The gas / particle stream from the mill is passed to the
classifier chamber via a static guide vane device 1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
.
The gas-solids mixture flows through the adjustable
guide vane 1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
and is presented to the radially bladed,
concentrically placed, classifier rotor 1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
20 21 22 23 24 25 26 27 28
.
The rotor accelerates the gas-solids mixture tan-
gentially. The centrifugal force produced rejects the
oversize material.
Through selection of the rotor speed, in combination
with the gas stream and its direction of flow, the
required separation grain size can be adjusted within
a wide range.
A special feature of this classifier type is the conti-
nuous re-classification of the particle stream rejected
by the rotor. When the particles are thrown outwards
by centrifugal force into the annular gap between
static guide vane and rotor they are again subjec-
ted to the upwards/inwards directed gas stream. In
this way agglomerated particles can be more easily
separated, so that they follow the product stream as
single grains and do not fall back onto the grinding
table with oversize material as apparent oversize.
Loesche_Zement_Rohmaterial_11-09.indd 21 17.09.12 11:31
22
1
1110
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
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Loesche hot gas generator
The perforated jacket combustion system developed
by Loesche in the mid 1960’s consists of a com-
bustion chamber of heat resistant steel with burner
muffle, and is well known in the market under the
name LOMA Hot Gas Generator. The LOMA Hot Gas
Generator has been used worldwide for decades
in many different types of thermal processes for
optimization.
Design and operation:
• The combustion chamber consists of heat resi-
stant steels – no refractory brickwork is necessary.
• When starting up the hot gas generator heat
losses are minimised since it is not necessary to
heat up refractory brickwork. A start at full load is
therefore possible.
• Very good thermal shock resistance and rapid
load changes with only a short delay.
• High cooling rate of the combustion chamber
prevents thermal overloading of following units.
AnEMERGENCYchimneystackisnotnecessary
in EMERGENCY-OFF SITUATIONS and when
starting and stopping.
• Accessiblewithinashorttimeforinspection
• Lowwear
• Short installationtimes, lowweight,smallspace
requirement. Can be installed in existing plants.
Complete preassembly is carried out – also for
larger LOMA combustion units.
Loesche hot gas generators are used where hot
gases are required for direct drying, e.g. in the
cement, steel, industrial minerals, ore, wood, cattle
food, agri-food and chemical industries.
Mode of operation
The process gas stream which enters the spiral
housing 1
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cools both the protective jacket housing
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and the perforated jacket 1
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. as a result of the
flow pattern. The process gas enters the interior of
the combustion chamber through the annular gap 1
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and holes in the perforated jacket, and mixes there
with the hot flue gases from combustion. At the same
time the flame and hot flue gases are kept away from
the perforated jacket.
Heating media
– Naturalgas,biogas,cokegas,blastfurnacegas
and other low calorific value gases
– Light and heavy oils, wood and lignite dust
LOMA Hot Gas Generator units are constantly being
developed and conform to current technical stan-
dards. More than 600 hot gas generators of this type
have been commissioned for a heat flow of between
100 kW and 64,000 kW.
Construction
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Burner
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Fuel
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Combustion air
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Burner muffle
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Spiral housing
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Perforated jacket
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Annular gap
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Protective casing
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Temperature control1
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Hot gas outlet
LOMA combustion unit type
LF 25 with a natural gas burner, 2005
Loesche_Zement_Rohmaterial_11-09.indd 22 17.09.12 11:31
23
Loesche rotary vane feeder
Feeding of Loesche mills is carried out via a rotary
vane feeder in order to prevent infiltration air ingress
into the mill interior.
Material is fed continuously from above via the inlet
hopper into every vane pocket of the slowly rotating
vane feeder. In order to reduce wear from the abrasive
feed stock the peripheral speed is low and the filling
level limited to 40%. Adjustable sealing strips on the
rotor prevent any large gaps between the wearing plate
of the housing and the rotor. The material is discharged
downwards into the feed chute of the mill.
Hot gas can be passed through the inside of the
rotary feeder to prevent material caking. It is easy to
dismantle for maintenance purposes.
Loesche_Zement_Rohmaterial_11-09.indd 23 17.09.12 11:31
24
Three well equipped laboratory LM 3.6 grinding mills
are available in the Loesche test plant for performing
standard grinding tests.
Technological development through practical laboratory grinding tests
One of the first steps in introducing new technologies
is the practical laboratory test.
Within the framework of our research and develop-
ment projects the following actions are carried out:
• Newmaterialsforgrindingoffuturemarket
requirements are examined
• Optimised mill settings for special products are
determined
• Plant components and process configurations
are optimised
• Newwearmaterialsandconceptsaretested
Our test plant is constructed in such a way that
various modes of operation and plant process confi-
gurations can be simulated in the tests.
Calibrated standard grinding tests for mill sizing
Loesche has many years of experience in designing
grinding mills. The most important prerequisite for cor-
rectly designed grinding mills is an exact knowledge of
the physical properties of the materials to be ground.
The most important characteristic values of a material
to be ground are the Loesche grindability factor and
the specific power demand in relation to a defined
fineness. Depending on the geological formation of
the material to be ground, materials with highly diffe-
rent properties are found in nature, even with materials
which appear visually to be similar.
Fully-automatic
operation with PLC
The Loesche test facility for raw materials testing,ResearchandDevelopment
Analysis possibilities
• Pure density determination with gas pycnometer
• Determination of mass-related surface according to Blaine
• Grain size analysis with Cilas laser granulometer
• Sieve analyses with Alpine air-jet screening method
• SieveanalyseswithRetschvibratingsieves
• Grindability according to Hardgrove
• Grindability according to Zeisel
• MicroscopywithZeissStemiSV11
• Drying ovens for moisture determination
• Coal testing (Cfix, volatile matter, ash content)
LM 3.6 laboratory mill
Loesche_Zement_Rohmaterial_11-09.indd 24 17.09.12 11:31
2525
Loesche – worldwide presence
Loesche is an export-oriented company run
by the owner, which was established in 1906
in Berlin. Today the company is internatio-
nally active with subsidiaries, representatives
and agencies worldwide.
Our engineers are constantly developing
new ideas and individual concepts for grin-
ding technologies and preparation processes
for the benefit of our customers. Their com-
petence is mainly due to our worldwide infor-
mation management.
This ensures that current knowledge and
developments can also be used immediately
for our own projects.
The services of our subsidiaries and agen-
cies are of key importance for analysis,
processing and solving specific project
problems for our customers.
Loesche GmbHHansaallee 24340549 DüsseldorfTel. +49 - 211 - 53 53 - 0Fax +49 - 211 - 53 53 - 500Email: [email protected]
BrazilLoesche Equipamentos Ltda.Rua México 119 sl. 190820031-145 Rio de Janeiro, BrazilTel. +55 - 21 - 22 40 79 00Fax +55 - 21 - 22 20 94 40Email: [email protected]
GermanyLoesche Automatisierungstechnik GmbHZum Pier 5244536 LünenTel. +49 - 231 - 98 70 10Fax +49 - 231 - 98 70 10 - 20E-mail: [email protected]
Loesche ThermoProzess GmbHUechtingstraße 19 / Gebäude D9D-45881 GelsenkirchenTel. +49 - 209 - 36 17 22 - 110Fax: +49 - 209 - 36 17 22 - 180 +49 - 209 - 36 17 22 - 190www.loesche-tp.de
IndiaLoesche India Pvt. Ltd.D - 83, Sector - 2Noida - 201301U.P., India Tel. +91 - 120 - 40 18 500 +91 - 120 - 24 44 205 - 207Fax +91 - 120 - 40 18 590 - 91 +91 - 120 - 24 43 327Email: [email protected]
People’s Republic of China Loesche Mills (Shanghai) Co., Ltd.No. 568, Jinhong Road(near No. 555, Chunhe Road)Baoshan District,201901 Shanghai, P. R. ChinaTel. +86 - 21 - 5180 6100Fax +86 - 21 - 5180 6101Email: [email protected]
Loesche Mills (Shanghai) Co. Ltd.5 Dongzhimen South Street Room 817-818, CYTS Plaza Dongcheng District, 100007 Beijing, P. R. ChinaTel. +86 - 10 - 5815 6205Fax +86 - 10 - 5815 6220 Email: [email protected]
RussiaOOO LoescheBerezhkovskaya Naberezhnaya 16a/2P.O. Box 97, 121059 MoscowRussian FederationTel. +7 - 495 - 988 50 81Fax +7 - 495 - 988 60 86Email: [email protected]
Socialist Republic of VietnamLoesche GmbH Viet Nam Representative office60 Nguyen Dinh Chieu Str.Dakao Ward, Dist. 1HCM - Ho-Chi-Minh City,Tel. +84 - 8 - 39 10 45 62Fax +84 - 8 - 39 10 45 26 E-Mail: [email protected]
South AfricaLoesche South Africa (Pty.) Ltd.55 Empire Road, Empire Park, Block C2193 Parktown, South AfricaTel. +27 - 11 - 482 29 33Fax +27 - 11 - 482 29 40Email: [email protected]
SpainLoesche Latinoamericana S.A.U.Condesa de Venadito 1, Planta 428027 Madrid, SpainTel. +34 - 91 - 458 99 80Fax +34 - 91 - 457 10 17Email: [email protected]
United Arab EmiratesLoesche Middle East FZEP.O. Box 262 622Jebel Ali, Dubai, U.A.E.Tel. +971 - 4 - 886 59 11 Fax +971 - 4 - 886 59 22Email: [email protected]
United KingdomLoesche Energy Systems Ltd.2, Horsham GatesNorth StreetHorsham, RH135PJ, United KingdomTel. +44 - 1403 - 223 101 Fax +44 - 1403 - 223 102 Email: [email protected]
USALoesche America, Inc.20170 Pines Boulevard, Suite 301Pembroke PinesFlorida 33029, USATel. +1 - 954 - 602 14 24Fax +1 - 954 - 602 14 23Email: [email protected]
Please visit our homepage at www.loesche.com for up-to-date information on our overseas companies.
25
1200181_LOES_huettensand_Zement_reprint_09/2012_V2.indd 25 25.09.12 10:32
Quartz (SiO2) 50µm Calcite (CaCO3) 20µm Aluminum oxide (Al2O3) 5µm
Dolomite 20µm(CaCO3•MgCO3)
Chalk (CaCO3) 2µm
Hydromagnesite + Calcite 5µm Clay 30µm
Air-cooled blast furnace slag 1µm Iron oxide, Titanium 30µm oxide and Orthoclase
Air-cooled blast 5µm furnace slag
Iron oxide (Fe2O3) 20µm
Hydromagnesite + Calcite 2µm
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Loesche_Zement_Rohmaterial_11-09.indd 26 17.09.12 11:31